Automatic Emergency Brake System

Emergency brake systems can prevent accidents entirely or at least make them less severe. An intervention by the automatic emergency brake system usually follows a certain pattern: a visual/acoustic warning is followed by brief light braking to get the driver’s attention and finally the full braking power is applied to come to an emergency stop. This final step of full emergency braking can also be implemented immediately if a sudden hazard occurs and prior warning is not possible, for example. When the automatic emergency brake system is activated, the vehicle overrules the driver.

In terms of user-oriented design, this begs the question: Is the driver able to manage and accept this unexpected automatic intervention?

Other more specific questions include:

  1. What is the maximum tolerable delay, in particular when the driver is alerted by the brakes briefly being applied?
  2. Is there a risk that the driver may react irrationally and jerk the steering wheel?
  3. How does the driver react if the automatic emergency brake system is activated for no apparent reason?
  4. How is control returned to the driver after the automatic intervention?

While the emergency braking system is engaged, the gas pedal is deactivated to prevent the brake from having to work against the acceleration. If the driver keeps their foot on the gas pedal, the deceleration force moving the driver forward as the vehicle slows down means that the pedal will be pushed down even further. The question is whether the driver is aware that their foot is on the gas pedal and that the vehicle will accelerate as soon as the automatic emergency brake system releases the brake.

A test drive lets drivers experience the automatic emergency brake system in action. After uneventfully passing a roadside structure several times, a cube-shaped object is suddenly thrown into the vehicle’s path, which activates the emergency brake. Answers to questions 1 and 2 can be deduced from the recordings of gas pedal engagement and steering wheel movements as well as the driver’s eye movements.

As a result of a number of trials, automatic emergency brake systems have been designed to require active changes between gas pedal, brake pedal, and gas pedal again for the driver to restart the vehicle (question 4).

The videos below show different tests to examine behavior during correct and false activation of the system.

Other Vehicles

Video: Vehicle to be overtaken suddenly shears into the lane of the test vehicle.

Bremsruck Fehlauslösung

Other Vehicles

Video: Vehicle in front brakes unexpectedly.

Other Vehicles

Video 2: Vehicle in front brakes unexpectedly

Sudden Obstacles

Video about testing human behavior in critical traffic situations.